Heretic was a lot of fun but the level design was hardly stellar.
An ever bigger issue is how bullet spongy the enemies are. I like Heretic, but it has problems.
I waited to play Amid Evil until full release, and I'm not disappointed - it far exceeded my expectations, actually, since I expected a semi-competent throwback, and instead got a really thoughtful piece of design.
Levels are quite impressive three episodes in. Amid Evil takes setting cues from Heretic and Hexen, sure, but it's actually closer to Quake in terms of everything else, and to the better community maps at that. Every level seems to be built around a clear idea, there's plenty of inventive geometry and solid variation which is further helped by the way the game is structured with shorter episodes. I think the 'arena' impression stems from how huge some of the maps get since you're going to get an arena for a boss fight, but that's about the extent of it - the gameplay relies on standard switch and key hunting. I haven't encountered any puzzles thus far, aside from your basic 'press three switches to activate whatever' Quake 'puzzles'. So no clearing arenas to progress, and no Hexen puzzle/backtracking bullshit (though you can go back to replay levels you finished). So far.
The weapons are fun to use, which is fairly odd for a fantasy shooter. Bonus points for managing to have the starter weapons still retain some utility even later on in the arsenal progression - that's a really cool touch. It's also nice to see someone still considers gunplay and enemy design to be intrinsically connected instead of seeing them as two elements you design separately and just slap together which is the impression I tend to get from most shooters. And there's no sponginess - this caught me by surprise more than anything else in Amid Evil.
If I had to nitpick I'd say the game would maybe benefit from a dynamic music system at times in the first few episodes - and I say 'at times' because even though the music is pretty firmly relying on atmosphere there's moments where this approach works both outside and during fights. Andrew Hulshult delivers once again.
Oh, and I'm not super stoked about the boss fights, but then again I'm not a fan of boss fights in first person shooters. They seem relatively decent here, but the genre doesn't lend itself to the concept all that well, I feel.